BACKGROUND Flap dehiscence is a common complication observed after Furlow palatoplasty, but its impact on speech outcome is unclear. This study aimed to test the hypothesis that flap dehiscence following Furlow palatoplasty significantly increases the risk of adverse long-term speech outcomes. METHODS This retrospective cohort study reviewed patients with soft cleft palate (SCP), submucous cleft palate (SMCP), or secondary velopharyngeal incompetence (VPI) who underwent Furlow palatoplasty from 2013 to 2023 at a tertiary hospital-based cleft center. The exposure variable was wound healing status, categorized as primary healing (without flap dehiscence), secondary healing (with flap dehiscence), or persistent fistulae formation. The location, size, and healing duration of flap dehiscence were also documented. The primary outcome was postoperative velopharyngeal function, assessed through standardized speech evaluations. Associations were analyzed using univariate and multivariate logistic regression models. RESULTS A total of 431 patients receiving Furlow palatoplasty were enrolled, with 12.5% reported flap dehiscence and 3.0% with persistent oronasal fistulae. For both primary cleft repair and secondary VPI correction, the occurrence of flap dehiscence and age at operation were identified as in significant correlation with postoperative velopharyngeal function. Patients with secondary healing demonstrated a higher rate of hypernasality and worse speech intelligibility. In addition, those with dehiscence size larger than 1cm2 demonstrated significantly higher rate of VPI than those less than 1cm2. CONCLUSIONS Flap dehiscence is a significant prognostic factor in long-term speech outcomes following Furlow palatoplasty. Wound healing monitor is necessary for the comprehensive evaluation of cleft repair techniques.